Tropical Lung

Tropical Lung

1. Histoplasmosis

   • Microbiology
     • The fungus exists in the mycelial form in nature.
   • Characteristics
     • H. capsulatum contains between five to seven chromosomes.
     • H. capsulatum is classified as a member of the family of Ascomycetes.
     • The organism has two morphotypes, the mycelial and yeast phases.
     • The former is present at ambient temperature and the latter at 37° C or higher.
     • The organism requires vitamins, thiamine, biotin, and iron
   • Clinical manifestations
     • Acute pulmonary disease:
       • Fever, productive cough, chest pain.
       • Minimal physical findings.
     • Acute cavity pulmonary disease:
       • Often asymptomatic
   • Diagnostic
     • Serology is useful for all but AIDS patients.
     • Acute infection:
       • Mild-moderate
         • H and M bands and complement fixation.
       • Moderate to severe
         • As above. Serum or urine antigen, or both, also may be positive in up to 70%. Bronchoalveolar fluid antigen may be useful. Culture of bronchoalveolar lavage fluid and silver stain of concentrated lavage fluid. Sputum culture.
     • Chronic cavitary:
       • H and M bands and complement fixation. Culture of bronchoalveolar lavage fluid and silver stain of concentrated lavage fluid. Sputum cultures.

2. Paracoccidiodes

   • Diagnostic
     • Direct microscopy and histopathology allow prompt diagnosis.
     • Acute/subacute:
       • The initial evaluation should include all of the following:
         • Imaging of affected areas to determine the extent of lymph node involvement
         • All patients should be evaluated by abdominal ultrasound or abdominal computed tomography
         • Direct examination and culture of specimens obtained by aspiration or biopsy of enlarged lymph nodes are routinely performed.
         • Serologic testing (preferably by quantitative immunodiffusion)
     • Chronic:
       • The initial evaluation of patients with suspected chronic paracoccidioidomycosis should include all of the following:
         • Since most patients have chronic pulmonary involvement, multiple lesions, and fibrosis, CT scanning is required to optimally characterize the lung lesions. A baseline chest radiograph is also useful since this modality can be used to follow response to therapy.
         • Direct examination and culture of sputum and/or biopsy specimens, depending upon sites of involvement
         • Serologic testing (preferably by quantitative immunodiffusion)
   • Microbiology
     • Paracoccidioides spp. (fungus)
   • Characteristics
     • Paracoccidioidomycosis is caused by Paracoccidioidesbrasiliensis,whichcontains four different phylogenetic lineages (S1,PS2, PS3,and PS4).
     • A new species,Paracoccidioides lutzii,has been recognized within P. brasiliensis and also causes paracoccidioidomycosis.
     • Paracoccidioides spp. are thermally dimorphic fungi,identified by multiple-budding yeast cells
     • These fungi exhibit slow mycelial growth for more than 20 days at 22° to 24° C. The yeast form appears ±10 days at 36° to 37° C.
     • These fungi are restricted to Latin American countries in unknown habitats.
     • The largest endemic areas are found in Brazil.
   • Clinical manifestations
     • Subclinical infection:
       • Considered to be a latent
       • Clinically asymptomatic process lasting for years after the initial fungal contact and that later may evolve to progressive, clinically manifested disease.
     • Residual form:
       • Characterized by the presence of sequelae originating in the previously infected fibrous tissues, mainly in the lungs but also in adrenal glands and mucosae.
     • Acute/subacute disease:
       • The lungs do not often reveal radiographic abnormalities, nor are the clinical manifestations obvious, despite the fact that P. brasiliensis is frequently detected in respiratory specimens.
     • Chronic progressive disease:
       • Characterized by important lung involvement and frequent lesions in the mucosae, skin, adrenal, and other sites
       • Constitutional symptoms fever, asthenia, general malaise, weight loss are regularly observed.

3. Coccidioidomicosis

   • Characteristics
     • Coccidioides has been found in desert soil and associated with animal burrows but is sparsely distributed, even within the most highly endemic regions.
     • On most laboratory media, growth by apical mycelial elongation is visible within a week.
     • It is now recognized as consisting of two species, Coccidioides immitis and Coccidioides posadasii
     • The mycelia consist of chains of cells that are approximately 3 to 5 microns in size.
   • Microbiology
     • Coccidioides spp. (fungus)
   • Diagnostic
     • Asymptomatic infection
       • Serologic testing that is performed as part of screening (eg, immunocompromised hosts) or as part of the evaluation of a pulmonary lesion.
     • Primary coccidioidal pneumonia
       • Serologic tests using EIA for IgM and IgG should be ordered first, if possible.
       • Immunodiffusion tests are generally performed to support the diagnosis when an initial EIA is positive.
       • Some labs offer immunodiffusion tests for initial evaluation.
   • Clinical manifestations
     • The first symptoms of the primary infection usually appear 7 to 21 days after exposure
     • Cough (73%)
     • Chest pain (44%)
     • Shortness of breath (32%)
     • Fever (76%)
     • Fatigue (39%)
     • Headache (21%)
     • Weight loss is also a common sign
     • Skin manifestations develop as part of the primary illness